Infra-Red Headphones

EE 63 February 1988 INFRA-RED HEADPHONES A low-cost infra-red transmitter and receiver to put an end to the inconvenience of an ever too short headphone cord. The infra-red band around 950 nm is ideal for short-range communication: no permits are required, there is very little interference, and active components for transmission and reception are readily available at reasonable prices. This article discusses a frequency modulated infra-red transmitter and associated re- ceiver capable of covering typical "living room" distances. The designs of trans- mitter and receiver are fairly simple, of- fering many ways for further exper- iments in infra-red communication. Readers interested in a theoretical background to the subject are advised to consult reference (0. The transmitter Figure 1 shows the circuit diagram of the transmitter. The design is based on only 2 integrated circuits: one for AF amplifi- cation and pre-emphasis (ICI), the other, IC2, for frequency modulation (FM) of the...